In a planarization process of a layer, for example, an etch-back process, a reflow process, a chemical mechanical polishing (CMP) process, and the like may be used. The chemical mechanical polishing process is advantageous for a wide area planarization.
In the chemical mechanical polishing process, a polishing target to be polished is mounted on a polishing apparatus, and a slurry composition containing a polishing agent may be provided between a polishing target and a polishing pad. At the same time, by rotating the polishing target in the state of being in contact with the polishing pad, the surface of the polishing target can be planarized. That is, the chemical mechanical polishing process is a process of mechanically polishing the surface of the polishing target by mechanically rubbing the polishing agent contained in the slurry composition and the surface protrusion of the polishing pad with the surface of the polishing target, and chemically removing the surface of the polishing target by causing the chemical components contained in the slurry composition and the surface of the polishing target to chemically react with each other.
Meanwhile, the oxidizer used in the slurry for polishing the metal layer may cause excessive oxidative etching of the metal layer. Such oxidative etching may intensify the surface roughness of the metal layer after the polishing process and may degrade the electric characteristics of the semiconductor device fabricated using the polishing process. Although slurry for polishing the metal layer with the lowered oxidizer content may be used, such slurry may have a problem of significantly lowering the polishing rate.